Metabolomic profile of milk fermented with Streptococcus thermophilus cocultured with Bifidobacterium animalis ssp. lactis, Lactiplantibacillus plantarum, or both during storage

In this study, the microbial interactions among cocul-tures of Streptococcus thermophilus (St) with potential probiotics of Bifidobacterium animalis ssp. lactis (Ba) and Lactiplantibacillus plantarum (Lp) in fermented milk were investigated during a storage period of 21 d at 4 degrees C, in terms of acidifying activity (pH and ti -tratable acidity), viable counts, and metabolites. A nontargeted metabolomics approach based on ultra-high-performance liquid chromatography coupled with mass spectrometry was employed for mapping the global metabolite profiles of fermented milk. Probiotic strains cocultured with St accelerated milk acidifica-tion, and improved the microbial viability compared with the single culture of St. The St-Ba/Lp treatment manifested a higher bacteria viability and acidification ability in comparison with the St-Ba or the St-Lp treatment. Relative quantitation of 179 significant metabolites was identified, including nucleosides, AA, short peptides, organic acids, lipid derivatives, carbohy-drates, carbonyl compounds, and compounds related to energy metabolism. The principal component analysis indicated that St treatment and coculture treatments displayed a complete distinction in metabolite profiles, and Lp had a larger effect than Ba on metabolic pro -files of fermented milk produced by cofermentation with St during storage. The heat map in combination with hierarchical cluster analysis showed that the abundance of metabolites significantly varied with the starter cultures over the storage, and high abundance of metabolites was observed in either St or coculture samples. The St-Ba/Lp treatment showed relatively high abundance for the vast majority of metabolites. These findings suggest that the profile of the metabo-lites characterizing fermented milk samples may depend on the starter cultures, and incorporation of probiotics may considerably influence the metabolomic activities of fermented milks.

Automated summary

This study investigated the microbial interactions among cocultures of Streptococcus thermophilus with potential probiotics in fermented milk during a 21-day storage period. Probiotic strains cocultured with Streptococcus thermophilus accelerated milk acidification and improved microbial viability. Metabolomics analysis showed distinct metabolite profiles in fermented milk produced by coculture treatments, with Lactiplantibacillus plantarum having a larger effect than Bifidobacterium animalis. Incorporation of probiotics significantly influenced the metabolomic activities of fermented milks.